The present invention relates to the audio-video recording of overhead projector based presentations.
Presentations to an audience are often made by a presenter with the aid of an overhead projector (OHP). One type of OHP has an upward-facing horizontal clear glass plate which is back-illuminated by the projector by a white light source so that projected light is directed upwards through the projection plate. Another type of OHP has an upward-facing mirrored plate which is front-illuminated so that light projected downwards onto the mirror is reflected upwards by the mirror. An object on either type of plate is thus illuminated so that light passing through or to one side of the object is projected upwards and then laterally onto a viewing screen. All such OHP plates are referred to herein as xe2x80x9cprojection platesxe2x80x9d.
In one type of presentation, the presenter lays a series of clear or translucent plastic sheets one at a time on the projection plate while giving a talk. The sheets may contain written information, drawings, graphs, photographs or any other type of visual information. Sometimes, the presenter may write on the sheets as part of the presentation. Such sheets are referred to herein as xe2x80x9cOHP transparenciesxe2x80x9d.
In another type of presentation, an active matrix liquid crystal screen is placed on the projection plate. The screen may be connected to a personal computer which then sends signals to the screen to activate pixels of the liquid crystal screen to display computer generated images. When activated, the pixels act as light shutters to alter the amount and colour of light passing through the screen. Such active matrix light shutters are referred to herein as xe2x80x9celectronic transparenciesxe2x80x9d.
OHP transparencies, electronic transparencies, and all other such objects which may be placed on an OHP projection plate as part of an audio-video presentation are referred to herein as xe2x80x9cviewable objectsxe2x80x9d.
If a person wishes to make a recording of an OHP presentation, then it is quite straightforward to make an audio-only recording of the presenter""s voice and to copy or print out paper images of the viewable objects, or to scan or capture these as computer-viewable images. However, a person listening to the audio recording while looking at the images may have difficulty in following the sequence of the images with the person""s voice. In addition, such an audio-only recording may miss important information, such as the presenter writing on the viewable objects, presenting viewable objects out of sequence, or pointing to parts of the viewable objects on the projection plate or on the projection screen.
One way to deal with this problem is to make an audio-video recording of the presentation with a camcorder set up to capture images of both the presenter and the OHP images as projected onto a screen. This, however, is not entirely satisfactory, as the video resolution of such recordings, at least for inexpensive camcorders, is insufficient to capture each projected image with adequate resolution. Preferably such resolution should be at least about 300 dpi for an A4-sized viewable object. Such resolution may be achieved by training a video camera exclusively on a projected image, but such a recording uses a significant amount of storage on a video recording medium, which is inconvenient to deal with even though such generally static images can subsequently be compressed.
It is an object of the present invention to provide a more convenient apparatus and method for making an audio-video recording of an OHP based presentation.
According to the invention, there is provided an apparatus for making an audio-video recording of an OHP based presentation, comprising an audio microphone, a logging means for logging when a presenter changes a viewable object on an OHP, and a recording apparatus, wherein: the microphone generates an audio signal from the audio portion of the presentation; the logging means is activatable to generate a marker signal indicating the change of viewable object; and the recording apparatus receives the audio signal from the microphone and the marker signal from the logging means to record said signals as audio data and marker data so that audio data is correlated with the marker data.
Also according to the invention, there is provided a method of making an audio-video recording of an OHP based presentation, using an apparatus comprising an audio microphone, a logging means for logging when a presenter changes a viewable object on an OHP, and a recording apparatus, wherein the method comprises the steps of:
a) using the microphone to generate an audio signal from the audio portion of the presentation;
b) changing a viewable object on a projection plate, and activating the logging means to generate a marker signal indicating the change of viewable object; and
c) using the recording apparatus to record the audio signal from the microphone and the marker signal from the logging means as respectively audio data and marker data so that audio data is correlated with the marker data.
Changes in viewable objects may then at a later time be correlated with changes in the viewable objects during the presentations.
The data may be analogue data, but is preferably digital data, for example digitally compressed audio data, and digital data indicating the points in the audio data at which viewable objects were changed by the presenter.
The apparatus may then, for example, record respectively the audio portion of the presentation, and the times during the audio portion of the presentation when viewable objects are changed.
The logging means may be manually activated by the presenter, or another person, whenever the presenter advances to the next viewable object, for example by pressing a button. It is preferable, however, if the logging means is automatically activated whenever the presenter changes the viewable object.
The logging means may indicate simply that the presenter has moved on to the next slide. Preferably, the logging means is adapted to detect when a presenter places an overhead transparency on a projection plate and/or removes said transparency from a projection plate.
If the order of the slides is known, then the correct slides can later be correlated with the marker signals.
There may be times when the presenter will present slides in other than a predetermined sequential order, for example digressing to a previously shown slide. It is therefore helpful if the marker signal contains information regarding the identity of the viewable object.
In a preferred embodiment of the invention, the logging means includes a sensor to detect whether or not an OHP transparency has been placed on the projection plate.
The OHP transparencies may comprise a clear or translucent sheet of plastics material. Such sheets may include non-transparent or non-translucent borders, for example an opaque plastic border along one or more edges, or a paper frame. The sensor may then be arranged to detect such a border or frame, either from its physical properties, or its optical properties.
The logging means may comprise an OHP alignment device, adapted to be placed or affixed atop a projection plate. The alignment device then includes at least one alignment edge against which a corresponding straight edge of an OHP transparency may be brought. The sensor is then adapted to detect the presence of the OHP transparency as the OHP transparency is aligned against the alignment edge. The alignment edge may be a continuous, straight alignment edge.
The sensor may be an optical sensor that senses a change in optical radiation mediated by the OHP transparency. The mediation of optical radiation may be by means of transmission through or reflection or scattering from the OHP transparency towards the optical sensor, and the optical sensor may detect either visible light, or invisible light, particularly infra-red optical radiation.
The logging means may include an integral light source arranged to transmit optical radiation to the optical sensor through/from the OHP transparency. It is preferred, however, if the optical sensor is arranged to detect optical radiation produced by an overhead projector when the OHP alignment device is on the projection plate.
It is possible, however, to use other types of sensor, for example a magnetic sensor adapted to detect a magnetic portion of an OHP transparency, particularly a magnetic strip, as the strip is moved relative to the magnetic sensor. Other types of sensor may alternatively be used, for example a pressure sensor, or a distance or gap sensor.
In any of these cases, it is particularly advantageous if the sensor is adapted to detect bar-encoded data on the OHP transparency.
Therefore, according to the invention there is also provided an OHP transparency for use with an apparatus according to the invention when this has means for sensing bar-encoded data, wherein the OHP transparency has along at least one edge thereof bar-encoded data.
For example, the bar-encoded data may be a series of dark/light or opaque/transparent or translucent stripes or areas. As the OHP transparency is placed on the projection plate, the movement of these stripes or areas is then detected by the sensor in the logging means.
In any event, it is particularly advantageous if each viewable object is individually distinguishable at the time the marker data is generated. If OHP transparencies are uniquely identifiable, for example by bar coding, then the logging means may capture the identity of each OHP transparency as this is changed. The presenter then need not be concerned with the exact order in which the OHP transparencies are shown. If the presenter digresses, and shows a previously presented OHP transparency, then this information will be captured with the marker information.
In a preferred embodiment of the invention, the logging means includes at least one pair of oppositely parallel arms between which an OHP transparency may be aligned when placed when on a projection plate. Such arms may have a channel or undercut into which an edge of the OHP transparency slides when it is placed on or removed from the projection plate.
In a particular preferred embodiment of the invention, the logging means includes four parallel arms arranged as a first pair of oppositely parallel arms and a second pair of oppositely parallel arms, the separation between the first pair of arms being greater than the separation between the second pair of arms, so that a rectangular OHP transparency can be placed on the projection plate in a landscape orientation between one pair of arms, and in a portrait orientation between the other pair of arms.
Each pair of parallel arms may then have a corresponding end stop for orienting an OHP transparency in a direction parallel to the arms. Preferably, the two pairs of arms and corresponding end stops are arranged so that the position of a centre point of a rectangular OHP transparency when aligned by one pair of arms and oriented by a corresponding end stop is the same as the position of the same centre point when the rectangular OHP transparency is aligned by the other pair of arms and oriented by the other corresponding end stop.
The apparatus may include a scanner for scanning an OHP transparency as this is being placed on a projection plate, or for scanning the OHP transparency as this is being removed from a projection plate. The scanner may be integral with or at least linked to portions of the apparatus on the projection plate, for example, automatically scanning OHP transparencies as these are removed from the projection plate.
In one embodiment of the invention for use with LCD light shutters and the like, the logging means is adapted to detect when a signal for an electronic transparency is transmitted for changing the viewable object on a projection plate.
The logging means may then be activated when a presenter changes a viewable object on an OHP, for example by activating a screen advance xe2x80x9cbuttonxe2x80x9d with personal computer presentation software.
The apparatus may then capture image data for the viewable objects in the presentation, and use the recording apparatus to record the image data together with the marker data so that the image data and marker data are correlated with each other.
The invention may also be used with a conventional video capture device, for example an inexpensive camcorder of modest resolution. This may be set with a wide field of capture, showing the presenter, overhead projector, and projection screen. If the presenter leans over the overhead projector, for example to write on an OHP transparency, or points to a particular part of an image projected onto the screen, this will be captured by the video capture device at the same time as the apparatus captures the audio data. The relatively low resolution video data can then be combined with the captured audio data, marker data and optionally also captured images of the viewable objects, for example being displayed side-by-side on a television screen or other video display unit, so that a person seeing the audio-video recording can see when and where the presenter is annotating or pointing to each of the viewable objects.